Browsing by Author "Temelkuran, B."

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Open Access
Defect structures in metallic photonic crystals
(A I P Publishing LLC, 1996-12-16) Özbay, Ekmel; Temelkuran, B.; Sigalas, M.; Tuttle, G.; Soukoulis, C. M.; Ho, K. M.
We have investigated metallic photonic crystals built around a layer‐by‐layer geometry. Two different crystal structures (face‐centered‐tetragonal and tetragonal) were built and their properties were compared. We obtained rejection rates of 7–8 dB per layer from both metallic crystals. Defect modes created by removing rods resulted in high peak transmission (80%), and high quality factors (1740). Our measurements were in good agreement with theoretical simulations.
Open Access
Exceptionally directional sources with photonic-bandgap crystals
(Optical Society of America, 2001-11) Biswas, R.; Özbay, Ekmel; Temelkuran, B.; Bayındır, Mehmet; Sigalas, M. M.; Ho, K.-M.
Three-dimensional photonic-bandgap crystals are used to design and fabricate uniquely directional sources and receivers. By utilizing the resonances of a Fabry-Perot cavity formed with photonic-bandgap crystals, we were able to create exceptionally directional sources by placing the sources within such a cavity. Very good agreement between finite-difference time-domain calculations and the experiment is obtained. Radiation patterns with half-power beam widths of less than 12 degrees were obtained. (C) 2001 Optical Society of America.
Open Access
Experimental demonstration of highly confined photonic crystal based waveguides
(IEEE, 2001) Bayındır, Mehmet; Özbay, Ekmel; Temelkuran, B.; Sigalas, M. M.; Soukoulis, C. M.; Biswas, R.; Ho, K. M.
The bending and guiding of the electromagnetic (EM) waves in highly confined waveguides was demonstrated. The electromagnetic waves were constructed by removing a single rod from a perfect three layer-by-layer photonic crystals. A layer-by-layer dielectric photonic crystal based on square shaped alumina rods was used with center-to-center separation of 1.12 cm. The results suggested the use of the layer-by-layer photonic crystal structure in the design of optoelectronic integrated circuits.
Open Access
Experimental demonstration of photonic crystal based waveguides
(A I P Publishing LLC, 1999-01-25) Temelkuran, B.; Özbay, Ekmel
We report the experimental demonstration of waveguides built around layer-by-layer photonic crystals. An air gap introduced between two photonic crystal walls was used as the waveguide. We observed full (100%) transmission of the electromagnetic (EM) waves through these planar waveguide structures within the frequency range of the photonic band gap. The dispersion relations obtained from the experiment were in good agreement with the predictions of our waveguide model. We also observed 35% transmission for the EM waves traveling through a sharp bend in an L-shaped waveguide carved inside the photonic crystal. (C) 1999 American Institute of Physics.
Open Access
Experimental investigation of layer-by-layer metallic photonic crystals
(Institution of Electrical Engineers, 1998-12) Temelkuran, B.; Altug, H.; Özbay, Ekmel
The authors have investigated the transmission properties and defect characteristics of layer-by-layer metallic photonic crystals. They have demonstrated experimentally that the metallicity gap of these crystals extends to an upper band-edge frequency, and no lower edge was detected down to 2 GHz. The defect structures built around these crystals exhibited high transmission peak amplitudes (100%) and high Q factors (2250). The crystals with low filling ratios (around 1-2%) were tested and were still found to possess metallic photonic crystal properties. These crystals exhibited high reflection rates within the metallicity gap and reasonable defect mode characteristics. A power enhancement factor of 190 was measured for the electromagnetic (EM) wave within planar cavity structures, by placing a monopole antenna inside the defect volume. These measurements show that detectors embedded inside a metallic photonic crystal can be used as frequency selective resonant cavity enhanced (RCE) detectors with increased sensitivity and efficiency when compared to conventional detectors.
Open Access
Guiding and bending of photons via hopping in three-dimensional photonic crystals
(IEEE, Piscataway, NJ, United States, 2000) Bayındır, Mehmet; Temelkuran, B.; Özbay, Ekmel
For the past decade, photonic crystals, also known as photonic bandgap (PBG) materials, have inspired great interest because of their novel scientific and engineering applications such as the inhibition of spontaneous emission, thresholdless lasers, optical circuits, antennas, waveguides, detectors, fibers, and so on. Creating defect states within the PBG are very important for such applications. Recently, we have reported the eigenmode splitting due to coupling of the localized defects and guiding of the electromagnetic (EM) waves through a periodic arrangement of such defects in three-dimensional (3D) photonic crystals. Although the modes of each cavity were tightly confined at the defect sites, overlapping between the nearest-neighbor modes is enough to provide the propagation of photons via hopping. We report on the observation of guiding and bending of EM wave through evanescent defect modes for three different PBG waveguide structures.
Open Access
Guiding, bending, and splitting of electromagnetic waves in highly confined photonic crystal waveguides
(American Physical Society, 2001) Bayındır, Mehmet; Özbay, Ekmel; Temelkuran, B.; Sigalas, M. M.; Soukoulis, C. M.; Biswas, R.; Ho, K. M.
We have experimentally demonstrated the guiding, bending, and splitting of electromagnetic (EM) waves in highly confined waveguides built around three-dimensional layer-by-layer photonic crystals by removing a single rod. Full transmission of the EM waves was observed for straight and bended waveguides. We also investigated the power splitter structures in which the input EM power could be efficiently divided into the output waveguide ports. The experimental results, dispersion relation and photon lifetime, were analyzed with a theory based on the tight-binding photon picture. Our results provide an important tool for designing photonic crystal based optoelectronic components.
Open Access
Highly doped silicon micromachined photonic crystals
(IEEE, Piscataway, NJ, United States, 2000) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Kavanaugh, J. P.; Sigalas, M. M.; Tuttle, G.
Summary form only given. Photonic crystals are periodic structures with the property of reflecting the electromagnetic (EM) waves in all directions within a certain frequency range. These structures can be used to control and manipulate the behaviour of EM waves. Although earlier work concentrated on building these crystals with dielectric materials, there are certain advantages of introducing metals to photonic crystals. First, metals offer a high rejection rate when compared to the dielectric crystals. Second, for microwave applications, the dimensions of metallic crystals can be kept much smaller than the minimum dimensions needed for a typical dielectric crystal. In the paper, we propose a method for the fabrication of layer-by-layer metallic photonic crystals. A similar method had been used by Ozbay et al. to fabricate dielectric photonic crystals using silicon wafers. We fabricated a new layer-by-layer photonic crystal using highly doped silicon wafers.
Open Access
A new detection method for capacitive micromachine ultrasonic transducers
(IEEE, 2001) Ergun, A. S.; Temelkuran, B.; Özbay, Ekmel; Atalar, Abdullah
Capacitive micromachine ultrasonic transducers (cMUT) have become an alternative to piezoelectric transducers in the past few years. They consist of many small circular membranes that are connected in parallel. In this work, we report a new detection method for cMUTs. We model the membranes as capacitors and the interconnections between the membranes as inductors. This kind of LC network is called an artificial transmission line. The vibrations of the membranes modulate the electrical length of the transmission line, which is proportional to the frequency of the signal through it. By measuring the electrical length of the artificial line at a high RF frequency (in the gigahertz range), the vibrations of the membranes can be detected in a very sensitive manner. For the devices we measured, we calculated the minimum detectable displacement to be in the order of 10 -5 Å/√Hz with a possible improvement to 10 -7 Å/√Hz.
Open Access
A new detection method for capacitive micromachined ultrasonic transducers
(IEEE, 1998) Ergun, A. S.; Temelkuran, B.; Özbay, Ekmel; Atalar, Abdullah
Capacitive micromachined ultrasonic transducers (cMUT) have become an alternative to piezoelectric transducers in the past few years. They usually consist of many small membranes all in parallel. In this work we report a new detection method for cMUT's. We arrange the membranes in the form of an artificial transmission line by inserting small inductances between the membranes. The vibrations of the membranes modulate the electrical length of the transmission line, which is proportional to the total capacitance and the frequency of the signal through it. By measuring the electrical length of the artificial line at a RF frequency in the GHz range, the vibrations of the membranes can be detected in a very sensitive manner. For the detector structure we considered a minimum detectable displacement in the order of 10-7 angstroms/√Hz is expected.
Open Access
Photonic crystal-based resonant antenna with a very high directivity
(American Institute of Physics, 2000-09-24) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Biswas, R.; Sigalas, M. M.; Tuttle, G.; Ho, K. M.
We investigate the radiation properties of an antenna that was formed by a hybrid combination of a monopole radiation source and a cavity built around a dielectric layer-by-layer three-dimensional photonic crystal. We measured a maximum directivity of 310, and a power enhancement of 180 at the resonant frequency of the cavity. We observed that the antenna has a narrow bandwidth determined by the cavity, where the resonant frequency can be tuned within the band gap of the photonic crystal. The measured radiation patterns agree well with our theoretical results. (C) 2000 American Institute of Physics
Open Access
Propagation of photons by hopping: A waveguiding mechanism through localized coupled cavities in three-dimensional photonic crystals
(American Physical Society, 2000) Bayındır, Mehmet; Temelkuran, B.; Özbay, Ekmel
A new type of waveguiding mechanism in three-dimensional photonic band-gap structures is demonstrated. Photons propagate through strongly localized defect cavities due to coupling between adjacent cavity modes. High transmission of the electromagnetic waves, nearly 100%, is observed for various waveguide structures even if the cavities are placed along an arbitrarily shaped path. The dispersion relation of the waveguiding band is obtained from transmission-phase measurements, and this relation is well explained within the tight-binding photon picture. The coupled-cavity waveguides may have practical importance for development of optoelectronic components and circuits.
Open Access
Quasimetallic silicon micromachined photonic crystals
(American Institute of Physics, 2001) Temelkuran, B.; Bayındır, Mehmet; Özbay, Ekmel; Kavanaugh, J. P.; Sigalas, M. M.; Tuttle, G.
We report on fabrication of a layer-by-layer photonic crystal using highly doped silicon wafers processed by semiconductor micromachining techniques. The crystals, built using (100) silicon wafers, resulted in an upper stop band edge at 100 GHz. The transmission and defect characteristics of these structures were found to be analogous to metallic photonic crystals. We also investigated the effect of doping concentration on the defect characteristics. The experimental results agree well with predictions of the transfer matrix method simulations. (C) 2001 American Institute of Physics.
Open Access
Reflection properties and defect formation in photonic crystals
(A I P Publishing LLC, 1996-08-05) Özbay, Ekmel; Temelkuran, B.
We have investigated the surface reflection properties of a layer-by-layer photonic crystal. By using a Fabry-Perot resonant cavity analogy along with the reflection-phase information of the photonic crystal, we predicted defect frequencies of planar defect structures. Our predictions were in good agreement with the measured defect frequencies. Our simple model can also predict and explain double defect formation within the photonic band gap.
Open Access
Reflection properties of metallic photonic crystals
(1998) Temelkuran, B.; Özbay, Ekmel; Sigalas, M.; Tuttle, G.; Soukoulis, C. M.; Ho, K. M.
We measured reflection-magnitude and reflection-phase properties of metallic photonic crystals. The experimental results are in good agreement with the theoretical calculations. We converted the reflection-phase information to an effective penetration depth of the electromagnetic waves into the photonic crystal. This information was then used to predict resonance frequencies of defect structures. A symmetric resonant cavity was built, and an experimental set-up limited reflection magnitude of 80 dB below the incident signal was observed at resonance frequency.
Open Access
Resonant cavity enhanced detectors embedded in photonic crystals
(American Institute of Physics, 1998) Temelkuran, B.; Özbay, Ekmel; Kavanaugh, J. P.; Tuttle, G.; Ho, K. M.
We report a resonant cavity enhanced (RCE) detector built around a three-dimensional photonic band gap crystal. The RCE detector was built by placing a monopole antenna within the localized modes of planar and boxlike defectstructures. The enhanced electric field around these defectstructures were then measured by a microwave detector and a network analyzer. We measured a power enhancement factor of 3450 for planar cavity structures. A Fabry–Perot cavity model was used to understand and predict resonant cavity enhancement in this structure. The tuning bandwidth of the RCE detector extends from 10.5 to 12.8 GHz, which corresponds to the full photonic band gap by the crystal. These RCE detectors have increased sensitivity and efficiency when compared to conventional detectors, and can be used for various applications. © 1998 American Institute of Physics
Open Access
A sensitive detection method for capacitive ultrasonic transducers
(American Institute of Physics, 1998-06-08) Ergun, A. S.; Atalar, Abdullah; Temelkuran, B.; Özbay, Ekmel
We report a sensitive detection method for capacitive ultrasonic transducers. Detection experiments at 1.6 MHz reveal a minimum detectable displacement around 2.5×10-4Å/ Hz. The devices are fabricated on silicon using surface micromachining techniques. We made use of microwave circuit considerations to obtain a good displacement sensitivity. Our method also eliminates the dependence of the sensitivity on the ultrasound frequency, allowing the method to be used at low audio frequency and static displacement sensing applications. © 1998 American Institute of Physics.
Open Access
Tight-binding description of the coupled defect modes in three-dimensional photonic crystals
(American Physical Society, 2000) Bayındır, Mehmet; Temelkuran, B.; Özbay, Ekmel
We have experimentally observed the eigenmode splitting due to coupling of the evanescent defect modes in three-dimensional photonic crystals. The splitting was well explained with a theory based on the classical wave analog of the tight-binding (TB) formalism in solid state physics. The experimental results were used to extract the TB parameters. A new type of waveguiding in a photonic crystal was demonstrated experimentally. A complete transmission was achieved throughout the entire waveguiding band. We have also obtained the dispersion relation for the waveguiding band of the coupled periodic defects from the transmission-phase measurements and from the TB calculations.
Open Access
Towards multimaterial multifunctional fibres that see, hear, sense and communicate
(Nature Publishing Group, 2007) Abouraddy, A. F.; Bayındır, Mehmet; Benoit, G.; Hart, S. D.; Kuriki, K.; Orf, N.; Shapira, O.; Sorin, F.; Temelkuran, B.; Fink, Y.
Virtually all electronic and optoelectronic devices necessitate a challenging assembly of conducting, semiconducting and insulating materials into specific geometries with low-scattering interfaces and microscopic feature dimensions. A variety of wafer-based processing approaches have been developed to address these requirements, which although successful are at the same time inherently restricted by the wafer size, its planar geometry and the complexity associated with sequential high-precision processing steps. In contrast, optical-fibre drawing from a macroscopic preformed rod is simpler and yields extended lengths of uniform fibres. Recently, a new family of fibres composed of conductors, semiconductors and insulators has emerged. These fibres share the basic device attributes of their traditional electronic and optoelectronic counterparts, yet are fabricated using conventional preform-based fibre-processing methods, yielding kilometres of functional fibre devices. Two complementary approaches towards realizing sophisticated functions are explored: on the single-fibre level, the integration of a multiplicity of functional components into one fibre, and on the multiple-fibre level, the assembly of large-scale two- and three-dimensional geometric constructs made of many fibres. When applied together these two approaches pave the way to multifunctional fabric systems. © 2007 Nature Publishing Group.
Open Access
Widely tunable resonant cavity enhanced detectors built around photonic crystals
(Society of Photo-Optical Instrumentation Engineers, Bellingham, WA, United States, 1999) Temelkuran, B.; Özbay, Ekmel
We report a resonant cavity enhanced (RCE) detector built around a three-dimensional photonic band gap crystal. We have demonstrated the resonant cavity enhanced (RCE) effect by placing microwave detectors in defect structures built around dielectric and metallic based photonic crystals. We measured a power enhancement factor of 3450 for planar cavity structures built around dielectric based photonic crystals. The tuning bandwidth of the RCE detector extends from 10.5 to 12.8 GHz. We also demonstrated the RCE effect in cavities built around metallic structures. The power enhancement for the EM wave within these defect structures were measured to be around 190. These measurements show that detectors embedded inside photonic crystals can be used as frequency selective RCE detectors with increased sensitivity and efficiency when compared to conventional detectors.